With these version bounds, the package successfully builds with GHC 8.6.5. The presence of character \160 in the source files also prevents nix from being able to build the haddocks successfully. If non-breaking space is necessary for the docs to be formatted nicely without unnecessary line breaks, I can try fixing the issue in the nix expression instead of here, but my attempts to do that so far have been unsuccessful.
With these version bounds, the package successfully builds with GHC 8.6.5. The presence of character \160 in the source files also prevents nix from being able to build the haddocks successfully. If non-breaking space is necessary for the docs to be formatted nicely without unnecessary line breaks, I can try fixing the issue in the nix expression instead of here, but my attempts to do that so far have been unsuccessful.